Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover read-only/idempotent/non-destructive/open-world, yet the description adds substantial behavioral context: the $0.01 cost, dual payment paths (api_key vs x402 explained in the response), and the reason to bind a follow-up tool (so a later gazette does not silently retire the value). This is exactly the kind of value-add annotations cannot supply.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads the cost and the resource, then detail. It is dense but each sentence carries information; the payment and follow-up clauses are long but functional rather than filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present, the description need not describe return values, and it is complete on everything else an agent needs: price, auth/payment options, scope, and post-call workflow. Nothing material is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds real meaning: api_key is optional and conditional on whether you have one, with card checkout at /pricing else x402, and the country scope is clarified as 'one country'. It adds some value beyond the schema's terse field descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource ('Country brief') and then enumerates exactly what is bundled (policy rate, VAT/GST, CPI, taxes, minimum wage, holidays) with per-series metadata (value, unit, effective/last-confirmed dates, source, confidence). This clearly distinguishes it from single-series siblings like get_series and get_series_history.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a concrete selection cue ('Cheaper than buying the series one by one') and prescribes a follow-up workflow ('bind get_changes ... or register_alert'). It stops short of naming a specific sibling to use instead when only one series is wanted, but the context is clear.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.